Kyle Dempster and Scott Adamson, well-known alpinists from Utah, were ascending a mountain peak known as Ogre II on Aug. 21 and were supposed to return to their base three days later

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The families of two U.S. mountain climbers missing for almost two weeks in Pakistan ended the search and rescue effort late Saturday.

Kyle Dempster, 33, and Scott Adamson, 34, well-known alpinists from Utah, were ascending a mountain peak known as Ogre II on Aug. 21 and were supposed to return to their base three days later, said Black Diamond Equipment, an outdoor company sponsoring Dempster.

They were trying to scale the 23,901-foot mountain's North Face, the company said.

Global Rescue, a travel risk and crisis management firm involved in the search, said a Pakistan military helicopter conducted flights over the the climbers' likely locations Saturday. A second helicopter was dispatched after the first one had to refuel, but there were no immediate signs of the men, NBC News reported.

The last confirmed sighting was of the men's headlamps on Aug. 22 by a Pakistani member of their base camp team. Neither climber was believed to be carrying satellite communication or messaging capabilities, Global Rescue added.